Portable crane with extendable boom

ABSTRACT

Portable crane with extendable boom of concentrically and eccentrically disposed telescoping tubes in which the first section is a rigid, high-strength square tube and the remaining sections are of progressively reduced diameters with a large diameter cylindrical tube as a second section defining with the first section triangular channels therebetween at the four corners to house sheaves and cable flights of an extension cable system that provides a mechanical advantage greater than two to one for extending the second section and the remaining telescoped tube sections proportionately.

United States atent Hi ach Feb. 1 1972 [54] PORTABLE CRANE WITH 2,571,858 10/1951 Garland ..212/55 EXTENDABLE BOOM 2,668,625 2/1954 Garland... .....2l2/55 2,675,211 4/1954 Regoord ..52/121 [72] Inventor: WIlburn L. HIppach, San Gabnel, Callf. 3,248,331 5/1966 Jones h 52/121 [73} Assignee: Bliss & Laughlin Industries, Incorporated, 3,465,899 9/ 1969 Reuter ..212/55 oakbmck FOREIGN PATENTS OR APPLICATIONS [221 led: mg-1,1969 160,027 3/1921 Great Britain .52/121 211 App]. No 46,825 43,819 7/1938 Netherlands ..52/121 Primary Examiner-Harvey C. Homsby and Thomas n [58] Field of Search ..212/55, 59, 144; 55220111158, 111271, 57 ABSTRACT Portable crane with extendable boom of concentrically and eccentrically disposed telescoping tubes in which the first sec- [56] References CIted tion is a rigid, high-strength square tube and the remaining UNITED STATES PATENTS sections are of progressively reduced diameters with a large diameter cylindrical tube as a second section defining with the i Heckart first Section triangular channfils therebetween at the four COP 2l37743 1/1938 ners to house sheaves and cable flights of an extension cable 2'740504 4/1956 system that provides a mechanical advantage greater than two 3000473 9/1961 to one for extending the second section and the remaining telescoped tube sections proportionately. 7222552 3/1903 18 Claims, 18 Drawing Figures PATENTEU FEB I I972 SHEET 2 [IF 5 N V E /V TOR W/LBURN L. H/PPA CH M 1 voim Attorneys FIG. 6

PATENTEDFEB H972 3.638.806

SHEET 3 OF 5 FIG. ii

//VVEA/7'0R W/LBURN L. H/PPACH Attorneys PORTABLE CRANE WITH EXTENDABLE BOOM BACKGROUND OF THE INVENTION In cable actuated extension booms of telescoping tubes, as shown in Garland U.S. Pat. No. 2,668,625, the successive tubes are of progressively smaller diameters. The first tube is the largest and is mounted on a stationary or portable base for angular movement both horizontally and vertically. Each successive tube is sufficiently smaller in diameter than the next larger tube that there is sufficient clearance between them when they are arranged eccentrically to pass cable flight between them at the greatest clearance, preferably along the top of each smaller tube. The cable system is one in which each tube intermediate the end tubes carries a vertical sheave at its outer end which receives a loop of cable therearound whose leads are fastened at one end to an upstanding anchor on the outer end of the next larger tube and the other end extends through said clearance therewith and is fastened to the inner end of the next smaller tube whereby the endwise movement of all telescoped tubes is proportional when the second tube is power-moved in the first tube. The last tube carries a sheave for the load hoist line which extends through the center of all tubes.

Since extension movements of the telescoping tubes are proportional and additive as to length, it is desirable to have the extension function quite sensitive as well as strong. This may be accomplished by high-ratio mechanical advantages involving a number of sheaves and enables the use of economical prime movers actuating the second largest tube to move the others.

The relative size of the cables and the clearance between graduated telescoping tubes to accommodate the cables has been a compromise in that the larger the cable size, the greater the clearance required between graduated tubes. Consequently, the smaller will be the successively smaller tubes and the lesser is the boom strength at the outer end of the boom. Moreover, even if larger cable sizes can be accommodated, it has not been convenient to use sheaves of the diameters desired for such sheave sizes as are required to promote longevity of the cables. On the other hand, the larger the innermost tube in relation to the outermost tube, the lesser the clearances permitted between tubes, and then it follows that either smaller cable sizes are used with loss of cable lift strength and cable flights are multiplied with a greater number of sheaves, or fewer tubes are employed resulting in an overall loss of boom length.

In this connection, not only is a telescoping boom contractable to minimum overall length for travel on public thoroughfares, but its readiness and degree of extendability are directly concerned with reach and load lift strength in which the weight of the successively smaller tubes themselves is an important ever present weight factor. As the boom approaches vertical for hoist height, the weight of the telescoping tubes exerted on the first tube is added more directly to the weight of the working load on the boom regardless of extension length if there is any degree of boom extension at all, and as the boom approaches a horizontal orientation for reach, the extension of the tubes involves a frictional load for the cables, as well as an increasing weight leverage factor for the telescopic overlaps of successively lower tube sections. For maximum effectiveness, longevity and safety, great strength is highly desirable in the first two boom sections and the largest possible sizes and minimum numbers of sheaves and cable flights are important.

SUMMARY OF THE INVENTION In the present invention where the primary cable and boom support efforts are the greatest, the rearmost or first tube section is ruggedly made cross-sectionally square and the second tube section is cylindrical to telescope therein as supported and guided by slide pads at the points of substantial tangency leaving four semitriangular channels at the four corners. This not only provides greater strength, a longer effective boom length, and a rigid weight support point at the outer end of the first telescoping tube section, but also provides four comer channels for as many flights of large size extension cable and sheaves as may be desired. A large sheave on the outer end of the square tube receives the lead of the extension cable from the winch drum, returns it in one of two channels to the inner end where a second large sheave of a diameter greater than that of the second tube is journaled on the inner end of the second tube as disposed in the plane of the two channels. The cable is easily reeved around this sheave and the lead therefrom extends forwardly through the second channel to be reeved around an external sheave on the end of the square tube from whence it is returned through the second channel to terminate in an anchor on the inner end of the second tube. Thereby a pulley arrangement is provided having a 3 to l mechanical advantage from the winch to the lower end of the second tube for extending the boom.

If a 4 to 1 advantage is desired for further sensitivity or power, or both, in changing the plumb line position of the hoist line of the boom, a further reeving of the cable is made around another large sheave on the rear end of the second tube and back through a corner channel where it is terminally anchored at the front end of and on the square tube. Because of these channel spaces even higher mechanical advantages can be attained by further large sheaves and cable flights for which there is more than adequate space in the square tube and channels.

It will be appreciated that a wire cable in a system having mechanical advantages may be acceptable of lesser diameter and, with the mechanical advantages provided by the invention, the cable diameter and the largest sheave diameters available can be matched to provide the greatest longevity and safety for a cable which in many boom applications is much used in controlling the length of the boom and in elevating and placing heavy loads, as where a three-quarter ton load can be picked up 40 feet from the crane base and lifted to an -foot elevation within 10 feet of the crane turret axis by a crane boom rated to handle at 30 a one-fourth ton load located 80 feet from the turret. Without safety interlocks being applied a break in this cable would permit the whole boom to collapse.

An object of the invention is to provide a more versatile crane construction wherein the lowermost cylindrical tube of a telescoping tube boom can be telescoped within a stationary square or rectangular tube to increase the horizontal and vertical ranges of the boom without reducing its load handling ratings per se.

A further object is to provide a cross-sectionally rectangular or square tube of great strength upon which associated boom and load handling equipment including the hoist winch and extension winch power assemblies can be compactly mounted any place therealong on a flat surface without the presence or the weight thereof lowering the load ratings of the boom.

Another object of the invention is to provide a closeclearance antiroll control at the inner end of the largest cylindrical tube of the boom to preserve its torsional and flexure freedom throughout its full length at all times, and prevent radial lost motion therebetween under reversing boom torsion and deflection effects.

Another object resides in the relative movement outwardly of the effective outer rigid support point with respect to the telescoping tubes during shortening of the boom by the outermost rigid support point of the square tube remaining fixed for the shortening boom as the innermost rigid support point for the innermost cylindrical tube moves inwardly. This is accomplished without impairing flexures of the tubes throughout their lengths as the overlapping relationship of all the tubes proportionately increases when the boom is shortened. Thereby, after the boom reaches half its length, the outwardly located rigid point of support rapidly increases the rated load lifting capability of the crane with a factor progressively doubling the work strength of the boom twice in the last half length of its shortening movement.

A further object of the invention is to provide by way of example, a more versatile crane performance characterized, by a greater capability and extended utility in which the boom at 45 inclination will handle over a given small area at least l times the load that is rated to be maximum for a larger area, which larger area is 50 times the size of the small area; the maximum load for the smaller area being based upon a 20 foot working radius and the maximum load for that radius being less than one-half the maximum load rating for the crane at a -foot working radius.

A further object of the invention is to double the load lifting capacity of what may be considered to be a conventional boom of graduated telescoping tubes and also increase its work area 30 percent at 45 inclination.

The invention is also characterized by an improved boom which is readily assembled and serviced; easily reeved, lubricated and maintained; and sufficiently flexible to indicate degree of load strain for safe operation visually below overload conditions.

Other and further advantages and objects will become apparent from the description which follows of the drawings in which:

FIG. 1 is a side elevational view in partial perspective of a crane and the boom thereof embodying the invention as illustrated with the telescoping tubes partially extended;

FIG. 2 is an enlarged fragmentary perspective view partly in elevation showing the overlap of the three largest tubes illustrating an embodiment of the invention;

FIG. 3 is a diagram of the cable system of the book portion shown in F IGv 2 having a 3 to l mechanical advantage;

FIG. 4 is a spread diagrammatic view of the sheave and cable arrangement for the boom shown in FIG. 1;

FIG. 5 is a partially cutaway view of the boom portion shown in FIG. 2;

FIGS. 6, 8, 9, 10, 11 and 12 are enlarged sectional views taken on lines 6-6, 8-8, 9, l010, 11-11 and 12l2, respectively in FIG. 5;

FIG. 7 is a perspective end view of the rear end of the first extendable round tube with square end plate and slide bearings which slide within the square tube;

FIG. 13 is a central vertical sectional view taken on line 13 of FIG. 11 telescoping tubes of the boom located outwardly beyond the square tube;

FIG. 14 is a perspective view of the rear end of one of the tubes shown in FIG. 13;

FIG. 15 is a view similar to FlG. 3 of a modified cable system providing a 4 to l mechanical advantage in the extension cable system;

FIG. 16 is a perspective view of the boom structure employing the cable system shown in FIG. 15;

FIG. 17 is a side elevational view of the fully extended crane and boom for maximum reach showing the deflection thereof under conditions approaching maximum load weight conditions as sighted by an operators eye;

FIG. 18 indicates the telescopic overlap of the tubes and the use of at least one end-stop at a sliding joint when desired either to control or supplement an automatic extension arrest control when the boom is fully extended.

More particularly the crane as shown in FIG. 1 comprises a base assembly 11 welded or bolted to a platform such as a vehicle bed 12 and has a ball race slewing ring assembly 13 thereon that rotatably supports a turret assembly 14 that carries the boom 15. Two heavy side-frame plates 16 on the turret extend upwardly to carry at approximately eye level a horizontal gudgeon pin 17 upon which a winch housing 18 supporting the boom is journaled for power driven movement in a vertical plane through an arc of approximately 90. The boom 15 of the invention includes a cross-sectionally square or rectangular stationary tube 22 rigidly secured to the winch housing 18 with both ends open and extending almost to the gudgeon pins. One or more eccentrically disposed telescoping tubes are received in the square tube 22. The five tubes 30, 31, 32, 33 and 34 are shown that are graduated down in size in that order and the largest one is circular with an outside diameter slightly less than the inside minor dimension of the square tube 22 (see FIGS. 2, 9 and 10).

A control box with panel 20 is mounted on the turret l4 and the movement in the vertical plane is power driven by a semiself braking screw jack assembly 19. The screw portion 23 of the jack assembly 19 is pivotally anchored by pin 24 at one end to a bracket 25 supporting both the tube 22 and the boom assembly 15 and the power-rotated nut 26 on the other end is pivotally gimbaled to the turret frame at 27. The screw and nut are self aligning and a self-applying brake (not shown) assures the locking of the nut against rotation between operations thereof.

The extension cable winch assembly is secured on top of the square tube 22 by two heavy side plates 36 and includes a prime mover and gearing (not shown) and a winch drum 37 rotatably supported thereby at journals 38. A cover plate 40 completes the housing with an opening 41 for the extension cable 42 from the drum. The extension cable drum 37 being mounted on the top side of the square tube 22, the first flight of the extension cable 42 not only extends directly through the opening 41 and externally along the top to the front end of the square tube 22 but all auxiliary equipment is conveniently located where it can be serviced and will permit vertical positioning of the boom. Tube 22 being open at both ends, as mentioned, receives the hoist cable 44 centrally through the boom directly from the hoist cable drum 49 which in turn is mounted within the rear end of the winch housing assembly 18.

As shown in FIGS. 6, 7 and 16. an essentially square plate 46 is welded to the rear end of the circular tube 30 to slidably lit with relatively close clearance in the square tube 22. This plate supports the tube 30 against relative rotation in the square tube with a sliding clearance and against the upper wall of the tube 22 throughout the major portions of its telescopic movement. At the outer end of the square tube 22, the cylindrical tube 30 is slidably supported on a bearing slide block 47 (FIG. Ill) that is secured on the bottom side 48 of the square tube 22 with its upper face 50 concave to cradle the circular wall of the cylindrical tube 30 in slidable weight-bearing guided relationship. The bearing block 47 is bolted in place and side guide spacers 61 on sidewalls 53 and a top guide spacer 52 on the upper wall 54 are also provided and bolted in place on the remaining walls, respectively, so that the tubes can be easily installed, serviced, and dismantled when occasion required.

With this arrangement not only are four triangular channels 55, 56, S7 and 58 provided between the tubes 22 and 30 at the four corners, each of which is capable of receiving a large number of flights of desirable size extension cable 42 in them that is accessible at both ends, but idler sheaves 64 can be journaled on the rear of the circular tube 30 to move within the square tube 22 having a slightly less diameter than the inner dimension of the square tube to handle the cable flights, yet greater than the diameter of the circular tube 30.

The words square" and circular as used herein in connection with the structural shapes of the tubes 22 and 30, respectively, indicates the preferred shapes because of economy and strength, but they include any telescoping tubular members of different cross-sectional configurations wherein the major dimension of the inside one is less than the minor dimension of the outer one to provide between their walls two or more channels symmetrically arranged and spaced a distance to receive parallel cable leads from a sheave that is received within the larger tube and mounted on the end of the smaller tube.

As shown in FIGS. 4, 8, 10, 25 and 16 full size sheaves 59 and 61 can be mounted at the forward end of the square tube 22 and at the upper corners whereby the grooves at their lower margins are tangentially in line with cable flights 62 and 63 in the triangular channels and 56. As will be seen later, the square shape geometry of the square tube 22 enables this mounting without interference with other boom parts and these sheaves 59 and 61 can be located beyond the outer end of the tube 22 as shown in FIG. 16, or within the tube 22 length. Moreover, if desired, sheaves 59a can be located on either one or both of the sidewalls 53a of the tube 23a at an angle as shown in FIGS. 15 and 16 with channel reentrant idlers 66. If located within the tube 22 length, they preferably are on the top wall 52 (FIG. with the sheave 60 extending inwardly through a slot 65 as will now be described in further detail.

More particularly with reference to FIGS. 2, 3, 8 and 10 the full size sheaves 59 and 61 are vertically mounted on horizon tal journal pins 67 carried by brackets 68 and 70 that are welded to the upper comers within the outer extremity of the square tube 22. The longitudinal slots 65 are provided in the tube wall 54 to receive the inner edges of the sheaves 59, 61, and 71 so that the lower portion of the sheaves extend therethrough into the two upper triangular channels 55 and 56, respectively to receive flights 43, 62 and 63, 64 of the extension cable 42 reeved around them. The bracket 70 for sheave 61 as shown in FIGS. 3, 5 and 8, extends rearwardly enough to carry an idler sheave 71 which also intercepts channel 56 through an elongated portion of the slot 65 for sheave 61 to receive the cable reeved over the top of sheave 61 and return it to the same channel.

A cross brace 72 interconnects the brackets 68 and 70 to rigidify them and is located close enough to the peripheries of the sheaves to hold the reeved cable in the sheave grooves. A second cross brace 73 located rearwardly of the brackets serves as an anchor bracket for secondary extension cable flights 74 to the tube 31.

In FIGS. 6 and 7, the square plate 46 on the rear end of the round tube 30 has a double-sided sheave bracket 75 adjacent to the upper side of the square tube 22 with a vertical journal pin 70 rotatably supporting the horizontally disposed sheave 60 which has reeved around it the loop of the cable leads 62 and 63 received from sheave 61 (FIG. 3). In this instance, the sidewalls 53 ofthe tube 22 hold the reeved cable in place.

The upper edge and face 78 of the plate 46 and bracket 75, respectively, have two support bearing assemblies 80 (FIG. 7) which engage the inner face of the top wall 54 of the square tube 22 (FIG. 5) when circular tube 30 is extended far enough that the boom weight of its exposed portion and the other proportionately extended tubes in it overbalances the boom weight of that portion thereof that is still in the square tube. This varies with boom inclination but is effective at all working inclinations. The plate 46 has a large aperture 81 over its lower portion to provide a channel for the load line 95 and rear access to the interior of tube 30 for inspection, reeving and lubrication ofall tubes. Also the plate 46 is apertured as at 82 and 83 to receive the cable leads as described wherever flights are provided in the channels. The openings 82 receive the leads to the sheave 60 (FIG. 7) while the opening 83 receives the tenninal end 64 of the cable 42 with a sleeve anchor 84 swaged thereon.

Accordingly, the reeving pattern of the boom extension cable 42 is shown diagrammatically in the spreadout plan view of FIG. 4 and the phantom view of FIG. 3, wherein the cable 42 extends forwardly with the first flight 43 from the winch drum 37 to and around the sheave 59 (FIG. 10) down into the channel 55 of the square tube and rearwardly by flight 62 to and round the sheave 60. From the sheave 60 the cable extends forwardly through channel 56 by flight 63 to and around sheave 61 and then is returned by the idler sheave 71 back into the same channel again and runs by flight 64 to the anchor 84 on the square plate 46 carried by the circular tube 30, thus providing a triple loop pulley system having a 3 to l mechanical advantage applying the extension effort of the cable 42 to the tube 30 through the sheave 60 and anchor 84.

If a greater mechanical advantage is desired, two sheaves 60 can be provided on the inner end of the circular tube 30, either side by side and both tangential to channels 55 and 56, with the anchors 84 located on the square tube at the front end of channel 56 or, as shown in FIGS. and 16, the sheaves 60 can be spaced apart for the second sheave 60A to be tangential to channels 57 and 58 with the anchor located on the square tube at the front end of channel 57. In this latter modification instead of the cable flight 64 being secured to the inner end of the circular tube 30, it is reeved around the second sheave indicated at 60A, extends by flight 85 through channel 57 to an extension of the spacer 51A in the square tube 22 and is terminally anchored at its front end. In both, four loops are provided which gives a 4 to l mechanical advantage. Up to four sheaves 60 can be used to provide an advantage up to 7 to I when employing a sheave system 59 and 66 in series between sheaves 59 and 61. The greater the mechanical advantage, the smaller the diameter of the cable 42 required, the less the gear reduction in the load winch drive and proportionately the greater the relative ratio of diameters between the cable and sheaves.

The structure and operation of the other telescoping tubes 31, 32, 33 and 34 is similar to that shown and described in the Garland Pat. No. 2,668,625, reference to which is hereby made. Briefly, the graduated reduction in diameters from tube to tube is sufficient to provide desired cable crescent clearance spaces 90, between successive tubes when they are arranged eccentrically as shown in FIGS. 11, 12 and 13. The lower adjacent sides of the circular tubes are virtually in contact with each other and the upper sides are widely spaced from each other at the top to clear the cable. At the rearward ends of the circular tubes there are crescent-shaped collars 91 (FIGS. 13 and 14) welded to the respective inner ends of the tubes, and dimensioned to be receivable with a sliding fit inside the next larger tube. The collars serve as spacers to position the telescoping tubes eccentrically as mentioned to assure maintenance of the described cable channel clearance between the upper wall portions of adjacent tubes. Each collar exerts an upward radial thrust on the next larger tube and each larger tube is provided with a suitable wear resistant quarterround bearing bushings 92 secured to a half-collar (FIG. 12) to reinforce its front end to bear the downward radial thrust of the next smaller tube.

It will be appreciated that rollers (not shown) can be used in place of bushings 92 to reduce considerably the extending friction but such is made less significant by the increased mechanical advantage attainable by the present invention.

The forward end of the outermost tube 34 of the boom 15 carries a bracket 93 supporting a hoist sheave 94 with its upper edge in alignment with the hollow space that is inside the boom, and the hoist cable 45 extending through the boom from the hoist winch drum 49 passes over this sheave 94 with a drop lead 95 having a weight fall and a grapple or grab means at its end, such as a hook 96. For certain applications a work platform (not shown) can be mounted on the end tube by bolts.

As shown in FIG. 17, a second load line winch 120 and control cable reel 121 are shown utilizing the rigidness of the square tube 22 as mounted on the flat bottom wall 48 thereof for nonflexing boom operation where fixed load position is important regardless of varying load conditions. The load line 122 is received on the gusset 99 located at the front end of the square tube 22 but can be located on other gussets where yield is desirable with a varying load. In the particular rigging shown the load line 122 supports a snatch block 123 supporting a control cable 124 for purposes well known in the art.

Referring to FIGS. 12 and 13, the circular tubes are held against relative rotation by angularly spaced tracks extending along the outer surface of each tube engaged on the top side by guide rollers 111 carried at the outer end of the next larger circular tube. This arrangement not only prevents relative rotation at each successive tube overlap, but being located at the outer end of each larger tube with the rollers on top they hold the smaller tubes slidable against the slide blocks 92. Grab eye gussets 99 are secured to each tube section for auxiliary hoist lines which may or may not be power driven.

The boom deflection sights are shown in FIGS. 12 and 13 wherein the rear sight 112 comprises the horizontal line on the upper edge of a lateral projection 113 on the square tube and the front sight 114 provides vertically spaced lines on a stepped projection to visually align a target sight IIS projecting laterally on the outer end of the tube receiving the outermost tube. As seen in FIG. 17, the projection line 116 indicates the theoretical centerline of the inclined boom while the projected curved line 117 indicates the fully extended boom deflection when lifting the lead 95 with a load approaching maximum for that reach. it will be observed that a straight sight line 118 of a human eye 120 from the rear sight to the target sight will index with the steps on the front sight 114 (FIG. 2) to apprise the operator of loading conditions if there is any question of possible overload. The length and rigidity of the square tube makes this possible with inexpensive and easily understood indicia. v

[n F 1G. 18 extension limit stops are shown in which lugs 119 are provided on the upper side of tubes 34 to engage the back side of the crescent collar 91 on tube 33 when the length of the telescoping arrangement between the tubes approaches approximately 8 diameters of the smaller tube 34 as a safety factor, it being appreciated that the lugs are located on opposite sides of the cable flights present at the overlap. in this connection it is also to be noted that if the boom is at a sufficientiy low inclination that it will not shorten when the brake on the extension boom winch is released, the weight fall 96 on the hoist cable can be drawn against the sheave bracket 93 and the tubes shorten by action of the hoist winch.

By way of example and not limitation, all tubes are of hard drawn 4130 steel and are approximately 16 to 24 feet long. The square tube is a fabricated high-strength tube of Moly- Boron Steel in which opposite walls are disposed vertically and parallel for rigid maximum lifting strength both under longitudinal compression and lateral deflection forces. The circular tubes graduate from the largest as follows: in. D. X 5/16 in.; 9 in. D. X A; 7% in. X A; 6 in. D. X A; to the smallest 4% in. D. X A. All are of hard drawn 4l30 steel. All primary sheaves of the square and round tubes are 18 cable diameters or more for iii-inch extension cable operated at 40 ft./min. which with a 3 to l advantage fully extends the boom in less than 2 minutes.

What is claimed is:

1. An extension boom crane comprising a base,

a turret rotatably mounted on the base for movement in a horizontal plane,

a boom support pivotally mounted on the turret for movement in a vertical plane,

a dual purpose boom substantially rigid for heavy duty short working range loads and appreciably flexing for a wide working range and high lifts, said boom comprising telescoping tubular members of different cross-sectional configurations wherein the inner tubular member is circular and the outer tubular member is square, the major dimension of the inner tubular member is less than the minor dimension of the outer tubular member,

means for securing the outer tubular member at one end to the boom support,

said outer tubular member having a planar sidewall portion and bordering corners parallel therewith spaced at least the width of the sidewall and the inner tubular member telescoping into said outer tubular member, and defining between their walls at said comers spaces defining parallel substantially triangular channels,

extension cable means having at least two spaced parallel flights received in the channels,

a large sheave,

bracket means on the inner end of the inner tubular member supporting said sheave and inner tubular member in the outer tubular member on said wall, the sheave being of a size and so located that the cable flights therefrom are disposed in said triangular spaces with their loop reeved 180 around said sheave.

2. The combination called for in claim 1 in which the diameter of the sheave is 18 diameters of the cable and is supported parallel to the wall portion of the outer tubular member included between the two channels.

3. The combination called for in claim 1 including a sheave supported on the outer end of the outer tubular member receiving the lead of one of the flights from said large sheave, and

an idler sheave receiving same and returning said one lead as a lead to another flight in the same channel,

one of said two flights being secured to the inner end of said inner tubular member.

4. A dual purpose extension boom for heavy duty short range work and a wide range for lighter work and comprising,

a solid wall substantially nonflexing outer square tube base member tiltably supported at one end and whose walls cross-sectionally define at least two included angles having a wall in common between them,

an inner circular tube telescoping in the outer tube in supported guided relation on central portions of walls of the square tube as spaced from the included angles and defining with said walls at the included angles enclosed cable receiving channels that are substantially triangular as located externally of said inner tube along and within said included angles,

sheave means,

bracket means carried on the inner end of said circular tube supporting said sheave means in the square tube below the inner end of the inner tube and centrally within a projection of the circular contour thereof with the groove of the sheave means tangentially aligned with said channels,

a single extension cable secured at one end to one of the tubes and having a plurality of flights two of which are through said channels and reeved in the groove around said sheave means,

and means carried by said outer tube for drawing the cable progressively around the sheave means and outwardly through the channel to extend the two tubes.

5. The combination called for in claim 4 in which the square tube is substantially rigid and the inner circular tube flexes under weight loads when extended from the square tube.

6. The combination called for in claim 4 in which said square tube is the outer tube and said circular tube is the inner tube and flexes under weight loads when extended, and

said cable drawing means includes a second sheave supported on the outer end of the outer tube with the cable extending tangentially thereto from the channel and reeved around it to provide a mechanical advantage with the first mentioned sheave means.

7. The combination called for in claim 4 including means holding the cable in place that is reeved on said sheave means in the sheave groove comprising a wall on one side of the included angle and guide openings through said bracket means aligned tangentially to the groove of said sheave means:

8. In an extension boom crane having a turret and a boom support pivotally mounted thereon,

a dual purpose boom for heavy duty short range work and a wide range for lighter work comprising a rigid cross-sectionally square tube secured to the boom support in an inclined position with a flat wall uppermost,

a circular tube slidably telescoped in said square tube and defining therewith two cable channels internally of the two corners bordering said flat wall,

sheave means mounted at the outer end of said rigid tube with one of the channels disposed tangentially thereto,

a sheave at the inner end of said circular tube approximately the same diameter as said circular tube,

bracket means carried on the inner end of said circular tube supporting said sheave with its groove tangentially to both of said channels,

cable means power driven at one end reeved around said sheave means and sheave with one lead thereof disposed in said one channel and the other lead in said other channel, and

means for securing to one of said tubes the end of said other lead that is remote from said sheave whereby said tubes are extended.

9. The combination called for in claim 8 in which said sidewall is disposed horizontally and said bracket means includes spaced guide openings aligned with the groove of said sheave to guide said leads tangentially to the groove of said sheave.

10. The combination called for in claim 8 in which said bracket means includes an element whose periphery follows the internal sectional contour of the square tube to engage the internal faces of the square tube walls to support the tubes against relative rotation.

11. The combination called for in claim 8 in which said rigid tube has a longitudinal slot adjacent to its end coincident with said one channel receiving the inner edge of the sheave means to a depth at which said sheave means is disposed tangentially thereto, said slot being located within the overlapping space remaining when the tubes are fully expanded.

12. A dual purpose extension hoisting boom for a heavy duty close working range load and a wide working range and high lifts comprising at least two telescoping tubes,

the larger one comprising a substantially rigid square tube,

a base member pivotally mounting said square tube on a turret member for movement in a vertical plane,

the second tube being the next smaller tube comprising a flexing circular tube telescoping with the square tube and defining therewith at least two spaced corner channels between the walls of the tubes,

a plurality of sheaves mounted on the outer end of the square tube each with the inner edge of its groove in alignment with a corner channel,

two of said sheaves being substantially coplanar, one to receive a cable lead from a channel at one end and the other to return the cable lead to the same channel at said one end,

bracket means mounted on the inner end of the circular tube supporting said circular tube on the wall of said square tube between said two corner channels,

sheave means carried by said bracket means for receiving one flight of cable from one of said sheaves and returning it around said sheave means to the one of said plurality of sheaves through another of said channels.

13. The combination called for in claim 12 including a third tube telescoping eccentrically in the second tube,

sheave means on the outer end of the second tube telescoping eccentrically in the second tube,

sheave means on the outer end of the second tube,

anchor bracket means supporting said two sheaves,

cable means connected to said bracket means anchoring one flight of a cable looped around said sheave means to be terminally received in said second tube and secured to the inner end of the third tube.

14. A dual purpose extension boom crane for heavy duty short range work and a wide range for lighter work and high lifts comprising a boom turret,

a boom base pivotally mounted thereon,

a rigid square tube secured to said boom base,

a circular tube telescoping in the square tube and having approximately the same length as the square tube,

guide spacers interengaging said tubes at the sides of the square tube,

said square tube and the circular tube defining substantially triangular channels at the comers of the square tube between said guide spacers,

bracket means on the inner end of the circular tube having means engaging under compression the inner face of the upper wall ofthe square tube,

an extension cable means interconnecting one of said tubes and a winch and including a sheave carried by the bracket means at the rear end of said circular tube within the square tube with the sheave grooves tangential to said triangular channels,

and a second sheave carried by the outer end of the square tube with its groove aligned at one edge with one of the channels, and

pivoted on the turret,

a dual purpose extension boom for heavy duty short range work and a wide range for lighter work and high lifts including telescoping tubes of graduated sizes,

a large size tube comprising a rigid square tube secured to said boom support,

a smaller tube comprising a flexing circular tube telescoping substantially coaxially with the square tube and defining therewith at least two corner channels,

bracket means secured to the inner end of the circular tube including a guide means engaging the walls of the square tube and support the circular tube slidably against rotation in the square tube and support means internally engaging the top side of the square tube slidably under compression,

a sheave mounted on said bracket means disposed in the plane of said two channels with its groove tangentially disposed in alignment with said corner channels,

a second sheave carried by the outer end of the square tube with its groove aligned at one edge with one of the channels,

second guide means at the outer end of the square tube slidably supporting said circular tube in weight bearing relationship, and

extension cable means reeved on said sheaves with the flights of cable disposed in said channels and power means connected to said extension cable means for shortening said cable means between said sheaves.

16. The combination called for in claim 15 in which said circular tube telescopically receives eccentrically disposed flexing tubes of graduated size including the third and fourth tube of said boom,

sighting means including two longitudinally spaced fixed sighting elements carried by said square tube and one sighted 0 element carried on one of the circular tubes to determine the degree of deflection of said flexing tube under a wide range working load,

range work and a wide range for lighter work and high lifts comprising:

a cross-sectionally square outer tube telescoping in the outer tube,

bracket means on the inner end of the circular tube intersupporting said tubes in guided relation on said three sides thereof to define therewith a plurality of cable channels between the tubes along the corners bordering one of the sides,

sheave means having a diameter almost equal to the width of said one of the sides mounted on said bracket means at the inner end of the circular tube parallel with said one side and with its cable receiving groove aligned with the two channels bordering said one side,

a sheave on the outer end of the outer tube with its cable receiving groove in alignment with one of the two channels,

a cable secured at one of its ends to one of the tubes and reeved serially around said sheave and sheave means with two flights disposed in the two channels,

tubes. 

1. An extension boom crane comprising a base, a turret rotatably mounted on the base for movement in a horizontal plane, a boom support pivotally mounted on the turret for movement in a vertical plane, a dual purpose boom substantially rigid for heavy duty short working range loads and appreciably flexing for a wide working range and high lifts, said boom comprising telescoping tubular members of different cross-sectional configurations wherein the inner tubular member is circular and the outer tubular member is square, the major dimension of the inner tubular member is less than the minor dimension of the outer tubular member, means for securing the outer tubular member at one end to the boom support, said outer tubular member having a planar sidewall portion and bordering corners parallel therewith spaced at least the width of the sidewall and the inner tubular member telescoping into said outer tubular member, and defining between their walls at said corners spaces defining parallel substantially triangular channels, extension cable means having at least two spaced parallel flights received in the channels, a large sheave, bracket means on the inner end of the inner tubular member supporting said sheave and inner tubular member in the outer tubular member on said wall, the sheave being of a size and so located that the cable flights therefrom are disposed in said triangular spaces with their loop reeved 180* around said sheave.
 2. The combination called for in claim 1 in which the diameter of the sheave is 18 diameters of the cable and is supported parallel to the wall portion of the outer tubular member included between the two channels.
 3. The combination called for in claim 1 including a sheave supported on the outer end of the outer tubular member receiving the lead of one of the flights from said large sheave, and an idler sheave receiving same and returning said one lead as a lead to another flight in the same channel, one of said two flights being secured to the inner end of said inner tubular member.
 4. A dual purpose extension boom for heavy duty short range work and a wide range for lighter work and comprising, a solid wall substantially nonflexing outer square tube base member tiltably supported at one end and whose walls cross-sectionally define at least two included angles having a wall in common between them, an inner circular tube telescoping in the outer tube in supported guided relation on central portions of walls of the square tube as spaced from the included angles and defining with said walls at the included angles enclosed cable receiving channels that Are substantially triangular as located externally of said inner tube along and within said included angles, sheave means, bracket means carried on the inner end of said circular tube supporting said sheave means in the square tube below the inner end of the inner tube and centrally within a projection of the circular contour thereof with the groove of the sheave means tangentially aligned with said channels, a single extension cable secured at one end to one of the tubes and having a plurality of flights two of which are through said channels and reeved 180* in the groove around said sheave means, and means carried by said outer tube for drawing the cable progressively around the sheave means and outwardly through the channel to extend the two tubes.
 5. The combination called for in claim 4 in which the square tube is substantially rigid and the inner circular tube flexes under weight loads when extended from the square tube.
 6. The combination called for in claim 4 in which said square tube is the outer tube and said circular tube is the inner tube and flexes under weight loads when extended, and said cable drawing means includes a second sheave supported on the outer end of the outer tube with the cable extending tangentially thereto from the channel and reeved around it to provide a mechanical advantage with the first mentioned sheave means.
 7. The combination called for in claim 4 including means holding the cable in place that is reeved on said sheave means in the sheave groove comprising a wall on one side of the included angle and guide openings through said bracket means aligned tangentially to the groove of said sheave means.
 8. In an extension boom crane having a turret and a boom support pivotally mounted thereon, a dual purpose boom for heavy duty short range work and a wide range for lighter work comprising a rigid cross-sectionally square tube secured to the boom support in an inclined position with a flat wall uppermost, a circular tube slidably telescoped in said square tube and defining therewith two cable channels internally of the two corners bordering said flat wall, sheave means mounted at the outer end of said rigid tube with one of the channels disposed tangentially thereto, a sheave at the inner end of said circular tube approximately the same diameter as said circular tube, bracket means carried on the inner end of said circular tube supporting said sheave with its groove tangentially to both of said channels, cable means power driven at one end reeved around said sheave means and sheave with one lead thereof disposed in said one channel and the other lead in said other channel, and means for securing to one of said tubes the end of said other lead that is remote from said sheave whereby said tubes are extended.
 9. The combination called for in claim 8 in which said sidewall is disposed horizontally and said bracket means includes spaced guide openings aligned with the groove of said sheave to guide said leads tangentially to the groove of said sheave.
 10. The combination called for in claim 8 in which said bracket means includes an element whose periphery follows the internal sectional contour of the square tube to engage the internal faces of the square tube walls to support the tubes against relative rotation.
 11. The combination called for in claim 8 in which said rigid tube has a longitudinal slot adjacent to its end coincident with said one channel receiving the inner edge of the sheave means to a depth at which said sheave means is disposed tangentially thereto, said slot being located within the overlapping space remaining when the tubes are fully expanded.
 12. A dual purpose extension hoisting boom for a heavy duty close working range load and a wide working range and high lifts comprising at least two telescoping tubes, the larger one comprising a substantially rigid square tube, a base member pivotally mounting said square tube on a turret meMber for movement in a vertical plane, the second tube being the next smaller tube comprising a flexing circular tube telescoping with the square tube and defining therewith at least two spaced corner channels between the walls of the tubes, a plurality of sheaves mounted on the outer end of the square tube each with the inner edge of its groove in alignment with a corner channel, two of said sheaves being substantially coplanar, one to receive a cable lead from a channel at one end and the other to return the cable lead to the same channel at said one end, bracket means mounted on the inner end of the circular tube supporting said circular tube on the wall of said square tube between said two corner channels, sheave means carried by said bracket means for receiving one flight of cable from one of said sheaves and returning it around said sheave means to the one of said plurality of sheaves through another of said channels.
 13. The combination called for in claim 12 including a third tube telescoping eccentrically in the second tube, sheave means on the outer end of the second tube telescoping eccentrically in the second tube, sheave means on the outer end of the second tube, anchor bracket means supporting said two sheaves, cable means connected to said bracket means anchoring one flight of a cable looped around said sheave means to be terminally received in said second tube and secured to the inner end of the third tube.
 14. A dual purpose extension boom crane for heavy duty short range work and a wide range for lighter work and high lifts comprising a boom turret, a boom base pivotally mounted thereon, a rigid square tube secured to said boom base, a circular tube telescoping in the square tube and having approximately the same length as the square tube, guide spacers interengaging said tubes at the sides of the square tube, said square tube and the circular tube defining substantially triangular channels at the corners of the square tube between said guide spacers, bracket means on the inner end of the circular tube having means engaging under compression the inner face of the upper wall of the square tube, an extension cable means interconnecting one of said tubes and a winch and including a sheave carried by the bracket means at the rear end of said circular tube within the square tube with the sheave grooves tangential to said triangular channels, and a second sheave carried by the outer end of the square tube with its groove aligned at one edge with one of the channels, and cable flights interconnecting said sheaves disposed in said channels within the corners of said square tube.
 15. In a crane having a rotatable turret and a boom support pivoted on the turret, a dual purpose extension boom for heavy duty short range work and a wide range for lighter work and high lifts including telescoping tubes of graduated sizes, a large size tube comprising a rigid square tube secured to said boom support, a smaller tube comprising a flexing circular tube telescoping substantially coaxially with the square tube and defining therewith at least two corner channels, bracket means secured to the inner end of the circular tube including a guide means engaging the walls of the square tube and support the circular tube slidably against rotation in the square tube and support means internally engaging the top side of the square tube slidably under compression, a sheave mounted on said bracket means disposed in the plane of said two channels with its groove tangentially disposed in alignment with said corner channels, a second sheave carried by the outer end of the square tube with its groove aligned at one edge with one of the channels, second guide means at the outer end of the square tube slidably supporting said circular tube in weight bearing relationship, and extension cable means reeved on said sheaves with the flights of cable disposed in said channEls and power means connected to said extension cable means for shortening said cable means between said sheaves.
 16. The combination called for in claim 15 in which said circular tube telescopically receives eccentrically disposed flexing tubes of graduated size including the third and fourth tube of said boom, said circular cube and said third tube each having sheave means at their outer ends, and cable means for each sheave means reeved thereon with one lead secured to the outermost end of said square and circular tubes, respectively, and the other ends secured to the innermost end of the third and fourth tube, respectively, to move the third and fourth tubes proportionately with said circular tube, said sheave means and cable means being located between the projected center lines of said two channels.
 17. The combination called for in claim 16, including visual sighting means including two longitudinally spaced fixed sighting elements carried by said square tube and one sighted element carried on one of the circular tubes to determine the degree of deflection of said flexing tube under a wide range working load, one of said elements having a graduated indicator correlated to beam load deflection.
 18. A dual purpose extension boom for heavy duty short range work and a wide range for lighter work and high lifts comprising: a cross-sectionally square outer tube telescoping in the outer tube, bracket means on the inner end of the circular tube intersupporting said tubes in guided relation on said three sides thereof to define therewith a plurality of cable channels between the tubes along the corners bordering one of the sides, sheave means having a diameter almost equal to the width of said one of the sides mounted on said bracket means at the inner end of the circular tube parallel with said one side and with its cable receiving groove aligned with the two channels bordering said one side, a sheave on the outer end of the outer tube with its cable receiving groove in alignment with one of the two channels, a cable secured at one of its ends to one of the tubes and reeved serially around said sheave and sheave means with two flights disposed in the two channels, and means carried by said outer tube to draw cable from said channels around said sheave to shorten the distance between the sheave means and sheave to extend the two tubes. 